Hydroxy-free acrylate resins are known articles of commerce. U.S. Pat. No. 4,327,013 describes the preparation of thermoset compositions using hydroxy-free acrylate resins. Such resins are typically co-polymerized with an ethylenically unsaturated monomer, especially styrene, to provide a comparatively inexpensive composition having relatively good mechanical strength properties. Hydroxy-free acrylate thermosets are further characterized by exhibiting low shrinkage upon molding and low water absorption.
Epoxy resins are similarly well known. Thermoset compositions prepared with epoxy resin normally have a higher service temperature and mechanical strength in comparison to acrylate resin thermosets, but are also generally more expensive. Furthermore, epoxy resins are prone to water absorption.
It is clear that a new material having a balance of the desirable properties exhibited by epoxy and acrylate resins would be a useful addition to the art. However, the two resins are prone to separate into two phases when attempts are made to co-cure them.
It has now been surprisingly discovered that a liquid adduct of a selected epoxy resin and a hydroxy-free acrylate resin may be prepared by reacting the epoxy and hydroxy-free acrylate in the presence of an amine or onium salt catalyst. The resulting adduct may be co-cured with a monoethylenically unsaturated monomer to provide a thermoset coating or molding composition.